1. Field of the Invention
The present invention relates to exposure systems including exposure apparatuses that expose substrates to light and fluid supplying apparatuses that supply fluid to the exposure apparatuses via flow channels, and relates to methods for manufacturing devices.
2. Description of the Related Art
Recently, higher productivity has been required for semiconductor integrated circuits such as ICs and LSI circuits. With this, power consumption of semiconductor exposure apparatuses has been increasing. On the other hand, circuit patterns have been increasingly miniaturized, and it has been necessary to maintain the environments inside the exposure apparatuses in a more stable state. In order to recover heat generated in an exposure apparatus and to reduce influences of, for example, temperature changes in a clean room in which the exposure apparatus is installed, a gaseous or liquid cooling medium serving as a fluid whose temperature is precisely controlled is supplied to the exposure apparatus. The air in the clean room contains chemical pollutants such as basic gases including ammonia and amine; acid gases including sulfuric acid, nitric acid, and hydrogen chloride; and organic gases including siloxane in trace amounts. When the air containing these chemical pollutants enters the exposure apparatus, the chemical pollutants can photochemically react with the exposure light source such as excimer laser beams that are short-wavelength ultraviolet rays, and can adhere to the surfaces of optical parts in the exposure apparatus, resulting in fogging of the parts. The adhesion of the fogging substances can cause a reduction or unevenness in the illuminance of the exposure light, and can preclude the exposure performance from being kept at a predetermined level.
Since it is necessary to reduce the concentration of the chemical pollutants contained in the air to one ppb or less, a chemical filter is used. The chemical filter removes the basic gases and the acid gases by using an ion-exchange reaction, and removes the organic gases by physically adhering the gases using activated carbon. The chemical filter can have various shapes. For example, a plurality of quadrangular chemical filters, each of whose sides is 600 mm and whose thickness is 60 mm, can be stacked in accordance with the target concentration of the chemical pollutants required for the installation environment. Since the chemical filter has a very high heat capacity, the thermal time constant thereof becomes extremely long, for example, from several minutes to several tens of minutes. Thus, although the concentration of the chemical pollutants in the air passing through the chemical filter can be reduced, there is a long time lag between the temperature at the entrance of the chemical filter and that at the exit of the chemical filter. Moreover, since the chemical filter absorbs or vaporizes moisture in the air when the humidity in the air before and behind the chemical filter is changed, the temperature of the air downstream of the chemical filter is changed by the heat absorption or the heat vaporization although the chemical filter has an effect on the removal of the chemical pollutants. Japanese Patent Laid-Open No. 2002-158170, for example, describes a technology for reducing the influences of temperature changes caused by changes in humidity in the vicinity of a chemical filter. Moreover, Japanese Patent Laid-Open No. 11-135429, for example, describes a technology in which an exposure apparatus and a fluid supplying apparatus are separated from each other.
The technology described in Japanese Patent Laid-Open No. 2002-158170 includes a temperature sensor disposed downstream of the chemical filter, and controls a heater disposed upstream of the chemical filter. Therefore, the response of the temperature control system is significantly limited by the long thermal time constant of the chemical filter. Furthermore, a temperature disturbance caused by the chemical filter, environmental changes superimposed downstream of the chemical filter, and a disturbance caused by, for example, changes in load in the exposure apparatus cannot be sufficiently reduced. In addition, the temperature sensor disposed downstream of the chemical filter controls the heater, and a temperature sensor for measuring the temperature of a cooler disposed upstream of the heater controls the cooler in this technology. Since the temperature control of the heater and that of the cooler are independent, the temperature cannot be precisely controlled when the temperature disturbance caused by the chemical filter and the temperature disturbance superimposed downstream of the chemical filter become so large as to exceed the heating capacity of the heater. As a result, the temperature stability of fluid supplied to the exposure apparatus cannot be maintained at a required level. Moreover, since the chemical filter is very large, the footprint of the exposure apparatus is increased, resulting in an increase in space occupied by the exposure apparatus in the clean room.
The technology described in Japanese Patent Laid-Open No. 11-135429 includes a temperature adjusting unit and a temperature sensor disposed downstream of the temperature adjusting unit in an exposure apparatus, and a temperature control unit controls the temperature of fluid supplied to the exposure apparatus. Furthermore, the value of the temperature sensor is fed back to a fluid supplying apparatus separated from the exposure apparatus such that the temperature of the fluid supplied to the exposure apparatus is controlled by operating a heater disposed in the fluid supplying apparatus. However, since the two temperature adjusting units are provided for the one temperature sensor, interference occurs in the control, preventing a precise temperature control.